1. Field of the Invention
The present invention relates to a method for producing iron-nitride powders in which nitrogen atoms are dissolved into .alpha.-iron. The resulting iron-nitride powders will be used as an excellent magnetic substance.
2. Description of the Related Art
A metastable intermetallic compound, Fe.sub.16 N.sub.2, comprising 16 iron atoms and 2 nitrogen atoms has a unit cell possessing body centered tetragonal (described as bet) crystal structure and exhibits excellent magnetic characteristics. This intermetallic compound is produced by vapor deposition of Fe in a reduced N.sub.2 gas atmosphere. (See J. Appl. phys., 67 (1990) 5126, Appl. phys. Lett., 20 (1972) 492))
Inventors have paid attention to the magnetic characteristics of the intermetallic compound and tried to develop a method for easily producing Fe-N alloy having the same magnetic characteristics as that of the intermetallic compound.
As for a compound comprising iron and nitrogen, Fe.sub.4 N has been known. The compound has .gamma.'-phase and is obtained by annealing .alpha.-Fe at temperatures between 500.degree. C. and 600.degree. C. in a nitrogen gas or NH.sub.3 gas atmosphere. Nitrogen atoms hardly dissolve into .alpha.-Fe at room temperature as described in the Fe-N binary phase diagram shown in FIG. 16. So, iron-nitride having body centered cubic crystal structure cannot be produced by the annealing.